Plenty of lens options. Perhaps a 300 2.8 with 1.4 and 2.0 teleconverters for the L series lenses ? Then you just need a mule to carry everything...

We don't do video, but I got my wife a 70-200 F2.8 and both of the teleconverters and she actually uses it quite a bit on wildlife. With the reduced size of the sensor on the camera (less than full frame) the 200 lens is already looking like a 300 F2.8. add the Teleconverter and it is a 600mm F4. Add the 1.4 converter and it is a 1000mm F5.6

Hello,
I need a bit of help. I'd like to be able to take high quality video of long range shooting..

Are you trying to document your hunts?
Simultaneous video of the shooter and the target?
See bullet impacts on paper or criters at long range? What's "long range" in yards for you?

"high quality" video won't happen with the camera more than a couple of hundred yards from the target in most atmospheric conditions. Do what film makers do and move the camera close to the action but not so close the perspective is obviously wrong.

If you have a location where you're likely to have game at a particular location you can set up a HDTV resolution camera within a hundred yards of where you expect the game to be. High resolution color IP cameras (including and especially 1920x1080 color CMOS cameras are quite reasonable and a 5.6 ghz ethernet microwave link with antennas are getting cheap too. (Ubiquity Nanobridge for example) It should cost under $1000 including a suitable lens for 100 yards. You can still take your shot at 800-1500 yards but record it from a much shorter distance. The camera and link can run for hours from a couple of motorcycle batteries. The receive end is a typical modern laptop which also does the recording.

You can make videos easily enough from 800 to 1500 yards but they won't be very clear. A $10,000, camera won't do significantly better than a $400 camera since the atmosphere in between will limit l the image quality.

It will shoot full HD at 30 frames per second in addition to its use as a camera. That is the one my wife has. Takes the exact same lenses. No matter who you get it from, quality glass costs money. The aformentioned 70-200 F2.8 lens has a 77mm diameter front element. Its price is relatively modest at $1300 and actually BH is not the cheapest place around, just the most reliable. Canon EF 70-200mm f/2.8L USM Telephoto Zoom Lens 2569A004 B&H

That combination cost about the same as my Savage 12 + Shilen barrel + Vortex scope. Only that it was money spent on my wife and not on me.